THE INCUBATION OF THE EGG 



193 



In the radiation type the air is poured into a drum, from 

 the surface of which the heat is given off by radiation. 



The third type is a combination of the foregoing in which 

 both diffusion and radiation are used as shown in Figs. 

 93 and 99. 



The contact type in common with the pure radiation type, 

 of which it is a modification, is largely obsolete. The plan is 



Fig. 95 



Hot-water incubator heated by pipes. (Courtesy of M. M. Johnson 

 Incubator Company.) 



to bring a radiating surface in actual contact with the eggs, 

 thus attempting to imitate nature. Mechanical and other 

 difficulties have so far prevented this type from being a 

 practical success. 



Hot-^ater Incubators.— Rot-w&tei incubators, of necessity, 

 depend upon radiation as the method of conveying the heat 

 into the egg chamber. This may be done by using a con- 

 tinuous tank which entirely covers the egg chamber, as in 

 Fig. 94, or by a tubular tank, as in Fig. 95. 

 13 



